CVE-2026-76641
Expat Out-of-Bounds Read via dtdCopy
- State
- Published
- Severity
- 8.7 High
- Published
- Aug 20, 2026
- Updated
- Oct 1, 2026
- Reserved
- Aug 19, 2026
Description
Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory corruption by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. A struct size mismatch between ELEMENT_TYPE members causes storeAtts to read the attIndex member past allocated memory boundaries, resulting in failure to normalize whitespace in non-CDATA attributes or a wild pointer dereference causing a segfault. This vulnerability was introduced by the fix for CVE-2026-66046.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | VulnCheck |
Weaknesses
- CWE-125 Out-of-bounds Read
Affected Products
| Product | Versions |
|---|---|
libexpatlibexpat |
|
References
- Pull Requestissue-tracking
- Patch Commitpatch
- https://www.vulncheck.com/advisories/expat-out-of-bounds-read-via-dtdcopythird-party-advisory
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